Preventing
Skin Damage in the Sun
by
Morten Bryhn, MD, Ph D
6/3/2002
Solar radiation is an important
environmental hazard with many deleterious effects on the
skin such as sunburn, photoaging and carcinogenesis. The
underlying mechanisms of ultraviolet radiation induced skin
damage are complex and incompletely understood. Omega-3
fatty acids show promising effects "from inside"
demonstrated in 3 clinical studies.
The
wish to get a suntan has two aspects: the medical and the
cosmetic. Synthesis of vitamin D important for calcium uptake
in the bones is important. Osteoporosis is common in the
Nordic countries where exposure to sun is mainly restricted
to a few, short summer months. And then there is the mental
part. Lack of sunlight makes us depressive. Light exposure
is widely used therapeutically as prophylaxis against depressions.
The suntan makes us look healthy, at least pale Kaukasians
living in the cold part of Mother Earth. The suntan also
protects us from getting sunburned creating a barrier against
the unwanted effects of ultraviolet radiation. So exposure
to sunlight makes sense in many ways.
But solar radiation is an important environmental hazard
with many deleterious effects on the skin such as sunburn,
photo aging and carcinogenesis. The most hazardous wavelengths
of solar radiation reaching the Earth are ultraviolet-B
(UVB) and ultraviolet-A (UVA). The more energetic UVB causes
most reactions in the superficial part of the skin layer,
while UVA reaches the deeper layer. UVB is primarily responsible
for sunburn and carcinogenesis, whereas UVA is believed
to be responsible for photo aging; and it also promotes
UVB carcinogenicity.
The
underlying mechanisms of ultraviolet radiation induced skin
damage are complex and incompletely understood. However,
free radicals and activators of the immune system such as
prostaglandins and cytokines are released in the process.
Skin protection against solar radiation is based on barrier
sunscreens. Originally, UVB-screening agents were used alone
because UVA was felt to be largely harmless. Sunburn was
reduced, resulting in higher UVA exposure, because individuals
could stay in the sun longer. It is now recognized that
UVA causes not only photo aging but also promotes the carcinogenicity
of UVB. So there has been focus on new ways of preventing
skin damage caused by solar radiation by combining different
measures. Omega-3 fatty acids have shown promising effects
"from inside" which have been demonstrated in
three clinical studies.
First
study
A research group in Liverpool, UK, has tested the effect
of omega-3 fatty acids in people especially susceptible
to solar radiation damage. In the first study 15 people
were given about 1.75g of omega-3 fatty acids daily for
6 months (1). Everyone was exposed to artificial UVB light
till reddening of the skin occurred before starting taking
omega-3 capsules. The same procedure was repeated at 1,
2, 3, 6 months and then medication was discontinued. A last
exposure was repeated at 8.5 months after the study started.
Skin biopsies were taken from six subjects. All subjects
completed the three months treatment and 10 continued for
a total of 6 months. The UVB dose causing eryteme increased
almost linear from the start to 6 months of treatment, and
was reduced to almost initial values after 8.5 months.
This
means that the tolerance towards UVB radiation improved
significantly. After one month of treatment the effect compared
to before the treatment started was statistically significant.
The tolerance improved continuously during 6 months of treatment
and disappeared rapidly after stopping omega-3 medication.
Analysis of fatty acids in skin biopsies showed an increase
in EPA and DHA, the most abundant omega-3 fatty acids in
fish oil.
Second
study
In a second study in the type of light-sensitive patients
13 people were treated with the same dose, 1,75mg, of omega-3
fatty acids as in the first study during three months (2).
As in the first study the tolerance to UVB light increased
significantly compared to pre-treatment values.
Third
study
In a third study on three patients with a rare skin disease
causing severe symptoms to sun exposure, the same dose of
omega-3 fatty acids was applied during three months. Clinically
significant improvements were obtained in two of the patients
(3).
These
studies document the positive effects of omega-3 fatty acids
on preventing sunburn from UVB exposure. An UVB cause not
only sunburn but also is responsible for dermal carcinogenicity.
Polyunsaturated fatty acids act as substrate for production
of imunno-activators like prostaglandins. There are two
different series of these activators: one type produced
by omega-6 fatty acids and another from omega-3 fatty acids.
The omega-6 derived activators are causing inflammatory
reactions while those from omega-3 fatty acids do not have
these effects. A balance between the intake of omega-6 and
omega-3 fatty acids is essential for obtaining normal immunological
reactions. However, the diet today contains large amounts
of omega-6 fatty acids from seed and vegetable oils and
red meat while the intake of omega-3 is low due to the fact
that people do not eat fatty fish very often. A study in
mice fed omega-6 fatty acids showed promoted photocarcinogenesis
and inflammation (4) while omega-3 fatty acids in another
animal study reduced sunburn and skin cancer (5). Increased
intake of omega-3 fatty acids will reduce the negative effects
of omega-6 fatty acids by competing for the same enzymes
producing the immunoactivators causing sunburn and perhaps
even photocarcinogenicity.
There
is definitely a need for new therapies and educational programs
to prevent negative effects from sun exposure (6). Safe
sun-bath should comprise three separate elements: 1) Reducing
sun exposure especially in the middle of the day when solar
radiation is maximal and using hats and T-shirts and other
garnaments 2) Sun-screens, preferably active against UVB
and UVA and 3) omega-3 fatty acids. Three grams of an omega-3
concentrate containing about 60% omega-3 fatty acids daily
will reduce the risk of getting sunburned. Optimally treatment
should be started early, at least one month before the sunbathing
season, and should be continued throughout the summer.
REFERENCES:
1) Rhodes LE et al. Dietary fish-oil supplementation in
humans reduces UVB-erythemal sensitivity but increases epidermal
lipid peroxidation
J Invest Dermatol 1994;103:151-154
2) Rhodes LE et al. Dietary fish oil reduces basal and ultraviolet
B-generated PGE2 levels in skin and increases the threshold
to provocation of polymorphic light eruption
J Invest Dermatol 1995;105:532-535
3) Rhodes LE and White SI. Dietary fish oil as a protective
agent in hydroa vacciniforme
Br J Dermatol 1998;138:173-178
4) Black HS et al. Influence of dietary omega-6, -3 fatty
acids sources on the initiation and promotion stages of
photocarcinogenesis
Photochem Photobiol 1992;56:195-199
5) Orengo I et al. Influence of dietary menhaden oil upon
carcinogenesis and various cutaneous responses to ultraviolet
radiation
Photochem Photobiol 1989;49:71-77
6) Rhodes LE. Topical and systemic approaches for protection
against solar radiation-induced skin damage.
Clinics in Dermatol 1998;16:75-82
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